Histamine Type-2 Receptor Antagonists (H2 Blockers)

If you mean to name three drugs that work as histamine-2 receptor antagonists, they are Cimetidine, Ranitidine and Famotidine. hope I understood your question correctly.

Frederick Leonard has written:

'Histamine antagonists' -- subject(s): Antihistamines

they block acid production of the stomach reducing the acidity

You can use histamine antagonists and/or immunosuppressants, since anaphylactic shock is just an overreaction of the immune system.